Blueprint sensitizer



Jul-1e 13 1.94@ ,c. A. CROWLEY Erm.. 2,350,991-

BLUE PRINT sEnsITIzER Filed Aug. 16, 1941 Patented June 13, 1944 2,350,991 BLUEPRINT SENSITIZER Clyde A. Crowley. Chicago, and George H. Goodyear, Wilmette, IIL Chicago, lll.,

assignors to The Huey Co., a corporation of Illinois Application August 1s. i941, lsei-n1 No.' 401,162

(ci. ss-c) 21 Claims.

'I'his application is a continuation in part of our application for patent on a Blueprint sensitizer iiled September 27, 1939, Serial Number 296,768.

It has long been the desire of manufacturers of sensitized paper of the type called blueprint paper, to obtain a sensitizer which, when coated on paper, will give a sensitized sheet having the following characteristics:

1. The paper must have a high .printing speed; that is, a short exposure will be suilicient to develop the desired color. I 1

2. The exposed sheet must have an intense blue color, and clear whites to give the desired contrast.y

3. When over-exposed, the blue color must be of good quality.

4. There must be no bleeding or running of color from the exposed portions into the unexposed white portions and white lines, even when the paper is badly over-exposed.

5. The sensitized paper must be capable of being stored under favorable conditions for periods up to two or three months, whereupon after development unexposed portions must contain a negligible amount of blue pigment.

For many years sensitizers have been formulated containing:

1. A light-sensitive ferric salt such as ierric ammonium citrate or ammonium ferrioxalate;

. A ferricyanide salt; and,` f

. Non-pgment-forming substances 4including other salts such as potassium oxalate, citrates, etc., which help keeping and washing properties, but do not themselves enter into the composition of the final pigment. In fact, their use in any amount decreases more or less the intensity and quality of the final blue pigment. When too much of non-pigment-forming substances is used, the color becomes unacceptable. Also, their presence markedly decreases the sensitivity of the` paper to light.

In practice, the light-sensitive ferric compound has been used in great excess over the quantity which is chemically equivalent to the ferricyanide salt (customarily potassium ferricyanide). This is necessary to obtain suicient light'l sensitivity. Ferricyanide is red in color and seems to filter out the shorterl wave lengths of light which are most eiective in causing the photochemical reaction. Thereforeto obtain high printing speed papers with this type of fermulation, the stoichiometric ratio of potassium ferricyanide to reducible ferric iron must be very small. As ferricyanide. is one of the essential components required to produce the final pigment, the maximum possible quantity of pigment, and hence Athe ponent.

. If a blueprint paper is even slightly over-exposed. ferrous iron in excess over the ferricyanide isi'ormed, and in the development process this ferrous iron'washes over into the unexposed portions, where it reacts with ferrieyanide to form blue pigment. 'Ihis is called bleeding. Also, the presence of excess ferrous' iron in the exposed portions adversely aie'cts the quality oi the blue pigment, giving it an undesirable slate or greyish cast. This is called burning out."

If. in the sensitizer. the ratio of potassium ferricyanide to light-sensitive i'erric compound is increased, the speed of the paper is decreased but the other desirable properties are gained in proportion. The sensitizers used by commercial blueprint paper manufacturers represent an unsatisfactory compromise between these inherent characteristics.

When a paper is exposed, the light-sensitive ferrie compound must be reduced to a ferrous compound, and the ferricyanide salt is reduced tc a ferrocyanide salt. 'I'hese react to form insoluble ferroferrocyanide (ferrous ferrocyanide). Development consists of washing of! the unexposed and excess chemicals, followed by the oxldation of the ferroferrocyanide to Prussian blue, and then washing oi the excess oxidizing agent, which is usually potassium bichromate.

' It has hitherto been suggested to use ferrocyanide salts in the sensitizer. When ferrocyanide was added to the customary formulation previously described, the following observations were made:

"Ihe speed of the paper was increased. However, in order to make it possible to wash the unexposed areas clean, it was necessary to add a much greater quantity of the ncn-pigment-forming substancesy such as oxalates, citrates, and phosphates to aid in washing and to use a substantial proportion of a ferricyanide salt. If the proportion of ferricyanide was decreased much below one-half the total quantity of iron-cyanides by weight, it was then necessary to add such a large proportion of non-pigment-forming substances as solubilizing agents that the quality of the final blue pigment was seriously impaired and the speed was reduced. When ferrocyanides were used in equal amountwith the ferricyanide, the necessary amount of non-pigment-forming substances for solubilizing markedly desensitized the paper.l Ihe result was that it seemed impossible to add more than a certain limited amount of ferrocyanide because the addition of greater quantities required additional ferricyanide which (l) light -sensitive ferric compounds such as ammonium ferrioxalate (ferrie ammonium oxalate), sodium ferrioxalate, sodium iron tartrate, ferrie ammonium citrate, or ferric potassium tartrate; and (2) iron-cyanogen compounds, which have in the past generally been -ferricyanides such as potassium ferricyanide, sodium ferricyanide, or sodium potassium ferricyanide, but which also include ferrocyanides such as potassium or lsodium ferrocyanide. All other substances which are included in a blueprint sensitizer are non-pigment-forming substances. Among the classes of non-pigment-forming substances which have been added to blueprint sensitizers are included: (1) buffering agents such as phosphates, borax, oxalates, and many other types ci compounds; (2) substances which are added to improve washing of the paper, which can be described broadly as solubilizing agents since they tend to make the unreacted pigment-forming chemicals more readily removable from the paper inwashing; these include sugars, such as dextrose or sucrose, oxalates, phosphates, citrates, and many others; (3) oxidizing agents such as nitrites and chlorates. which frequently serve no apparent purpose, although in the case' of papers containing ferrocyanides they will tend to increase ferricyanide at the expense of ferrocyanide; (4) binders, ,such as gums, starch, and the like, which are intended to prevent the sensitizer from soaking into the paper; (5) wetting agents, which are added primarily to aid in securing an even coat, but which may also ald in washing. This list by no means exhausts the tally of non-pigment-forming substances which have been proposed or used in blueprint papers. Some of these non-pigmentforming substances, as shown above, perform some useful function:e. g., buffer action or solubilizing; lhowever, in many instances, the non-pigment-forming substances must be regarded as inert from every aspect. In either case. the non-pigment-forming substances are completely inertso far as forming pigment is concerned; and when used in excessive quantities, they are deleterious to the quality of the paper. Their deleterious effect arises from two sources; first, they interfere with the light reaction and reduce thel speed of the paper, perhaps because they attenuate the pigment-forming substances as well as screening them from the light; and second, their presence in the pigmented areas after exposure imparts a dull, lifeless quality to the blue pigment in contrast to the brilliant blue formed when non-pigment-forming substances are absent or present only in moderate quantity.

Our invention consists of the discoveryl that when large quantities of ferrocyanide are used, approaching or exceeding the amount necessary for chemical equivalence to the light-sensitive iron compound, no ferricyanide salt is necessary to make the paper stableto storage, nor must such excessive-amounts of non-plgment-forming substances, including washing or solubilizing agents, be present that the quality of the ppal blue pigment is impaired.- Bieeding" and burnout" do not occur. Ferricyanide salts may be used if desired, but only as a control over the l printing speed of the paper, since sensitizers formulated with the above components only can be made so fast that they cannot generally be used in the usual present day commercial blueprinting practice.

Relatively small amounts of potassium ferricyanide exert ay verylarge effect in reducing the printing speed of sensitized papers.

Chemical equivalence is dened as two atoms of ferric iron -as light-sensitive ferric compound or compounds for each iron atom present as a 4ferrocyanideor ferricyanide salt. This is true because the final reactionproduct on the completely exposed paper is ferrous ferrocyanide 1'e+2[.'i'e(CN)sl4 or its equivalent. Under these conditions there can be no excess ferrous iron to cause bleeding or burn-out. As a matter of practical experience, it has been found that when there is onlyabout 60% of the ferrocyanide salt present necessary for chemical equivalence to the light-sensitive ferric compound, the highest speed papers so formed are substantially non-bleeding in commercial printing machines. This is probably caused by the fact that a proportion of the light-sensitive ferric compound is shielded from the light by chemicals and paper bers between it and the exposing lights, so that a portion of down the sensitizer and adds approximately the additional quantity of iron-cyanide salt necessary to insure substantially non-bleeding papers at the slower printing speeds.

At this point- Ie wish to vmake the following clear. When there is a sumcient quantity of ferrocyanide and ferricyanide salts present in the sensitizer to be chemically equivalent to the lightsensitive ferric iron compound present, there is no bleeding. Bleeding under such circumstances is impossible. Small reductions in this ratio of total ferrocyanide and ferricyanide salts to lightsensitive ferrie compounds do not cause bleeding under conditions of present day commercial practice. As the ratio of these salts is further decreased, bleeding eventually occurs and becomes increasingly severe as the ratio of these salts is still further reduced. As the ratio\of total ferricyanide and ferrocyanide salts to light-sensitive ferric iron compounds is decreased, it becomes necessary to add increasing quantities of nonpigment-forming substances for solubilizing, in order to insure complete washing of the unexposed areas and to make the papers stable in storagev A sensitizer in which ferrocyanide salt only is used, and in which itconstitutesv60% of the quantity chemically equivalent tothe light-sensitive ferric compound present, is'approximately the practical boundary for substantially nonbleeding papers. When less than this ratio of ferrocyanide is used, without ferricyanide salts being-present, the required quantity of non-pigment-forming substances required for ysolubilizing becomes excessive.

If ferricyanide is added to the sensitizer in addition to ferrocyanide,4 the ratio of ironcyanides to ferrie iron salts required for papers that are substantially non-bleeding in practice is greater. For slower papers in which ferricyanidevsalts form an appreciable part, for example, from about 1% to about 5% by weight, of the iron-cyanide salts, a total content of ironpaper and impair they quality of the. blue pigment.

It has been found that the pH of these sensitizing solutions is not'critical between reasonable limits. The pH must not be so high as to precipitate the iron from the light-sensitive ferric compound as ferric hydroxide or basic ferric compounds. 'Ihis pH varies with the nature and quantity of the solubilizingv salts present, being in general lower in the presence of phosphates and higher in the presence of citrates. A pH of 8.5 or 9.0 is approximately the upper limit.

When the pH is much below 4.0, it becomes more dimcult to stabilize the paper from the standpoint of shelf life; however, we do not wish to limit the practice ofthis invention, by any minimum pH value, as certain classes of blueprint papers falling within the definitions of this invention can be manufactured from sensi- 'tizers adjusted to pH values below a pH of 4.

Further evidence of the non-critical pH range is indicated by the following observations. The sensitizing coating has been washed, with distilled water, from satisfactory papers containing ferrocyanide salts. The pH of these washings has been found invariably to lie between a pH value of 5.5 and 6.9. In general, we have observed that regardless of the pH oi' the original sensitizing solution, the pH of washings removed from the sensitized sheet invariably falls between 5.5 and 6.9.

In order to illustrate diagrammatically the relationships among the three chemical compounds or their equivalents which actually enter into the formation of the final blue pigment, the accompanying composition diagram has been prepared. These three compounds are considered to be 100% of the materials entering into the photochemical reaction. Non-pigmentforming substances which may be present are not considered. The specific compounds represented in the diagram are potassium ferrocyanide, K4Fe(CN) s.3HzO; potassium ferricyanide, K1Fe(CN)s; and ammonium ferrioxalate,

These materials are represented in actual weight percent. Any other combination of compounds such as sodium ferricyanide, ammonium ferroin the triangle and parallel to line CIBv representl a ilx'ed percentage of compound A or potassium Y ferricyanide. 'Ihese lines are drawn at 10% intervals. Likewise, point B represents 100% by weight of ammonium ferrioxalate Lines parallel to side AC represent a given percentage of this compound. These lines are also shown at 10% intervals. Similarly, point C reprents 100% by weight of potassium ferrocyanide Lines parallel to side AB are drawn at 10% intervals to represent percentage of this compound.

Any sensitizer containing a ferrocyanide salt',l or mixture of ferrocyanide salts,- a ferricyanide salt or mixture of ferricyanide salts, and a lightsensitive ferrie compound or mixture of lightsensitive ferric compounds 'is represented by some specific point on this diagram. Using this diagram, therefore, it is possible to compare specifically as regards content of pigment-forming chemicals any sensitizers whose active components are ferrocyanide, ferricyanide, and lightsensitive ferric compounds.

Point Erepresents that composition ofpotassium ferricyanide and ammonium i'errioxalate which contains a chemically equivalent quantity of ferricyanide salt to light-sensitive ferrie compound; that is, one iron atom from the ferricyanide salt to two iron atoms from the light-sensitive ferrie compound. This point was calculated as follows:

Ammonium ferrioxalate has a formula weight of 446 and. contains one atomic weight of iron (55.84). Two formula weights of ammonium ferrioxalate (892) contain two atomic weights of iron. Potassium ferricyanide [(KaFe(CN)s] has a formula weight of Cil cyanide, and potassium iron tartrate may be apl plied to this diagram by using the corresponding chemically equivalent weights of the compounds used in plotting the diagram. Specic examples will be given later.

Any point within the triangle ABC represents a given composition of potassium ferrocyanide, potassium ferricyanide, and ammonium ferrioxalate. Point A represents 100% by Weight of potassium ferricyanide. 'Ihe farther-from A a given point may be, the less potassium ferricyanide there will be in the sensitizer, until should the given point lie upon the side CB, the sensitizer would contain only potassium ferrocyanide and ammonium ferrioxlate. Lines with- 329 and contains one atomic weight of iron. Therefore, 329 grams of potassium ferricyanide are chemicallyequivalent to 892 grams of ammonium i'errioxalate. See Table I.

Table 1 (Point E en diagram) Grains f Per cent KJFMCNM 329 27 (N HOxFe (CsolAHsO 892 73 Point D represents that composition of potasf slum ferrocyanide [K4Fe(CN)s.3HzO,' formula weight 422.33 and containing one atomic weight of iron] and ammonium ferrioxalate which contains a chemically equivalent quantity of ferrocyanide salt to light-sensitive ferric compound. See Table II for data.

Table II (Point D 0n diagram) Grams Per cent K4Fe (CN)|.3H3O 422 32. 2

(N H)|Fe(C|Q4)a.4H10 v-... 892 67. 8

` ferric compound, and

ately called the iron is contained in the ferricyanide salt and half in the ferrocyanide salt. See Table III.

Table HI (Point F on diagram) Grams Per cent K4Fe(CN)|.3H3O 422-Z-2=2ll 16. 6 KaFe(CN) 3294-2-164. 5 13. 0 (NH|);F6(C:O);.4H|O) 892 70. 4 1, 267. 100

The straight-line DFE on which these points D. E, and F lie represents all compositions of the above three compounds in which the iron-cyanide salts are chemically equivalent to the light-sensitive ferric compound and is, therefore. approprinon-bleed boundary. Bleeding cannot occur in sensitizers whose composition is represented by a point on this line or above and to the left of it. 4 Line NPM, .which is approximately parallel to the non-bleed boundary DFE, represents that composition of the above three compounds in which the totaliron cyanide content is 72% of the quantity required to be chemically equivalent to the light sensitive ferric compound present. 'I'his is approximately the practical boundary for substantially non-bleeding papers, except for very fast papers containing a very low percentage of ferricyanide, where the percent of iron cyanide may be somewhat lower.

Points N and M represent respectively 72% chemical equivalence of potassium ferrocyanide and of potassium ferricyanide to ammonium ferrioxalate; therefore the mass of potassium ferricyanate present at point M is (0;72X329) or 236 g. for a mass of 892 g. of ammonium ferrioxalate. Similarly at point N the composition is (072x422) or 304 g. of potassium ferrocyanide for a mass of 892 g. of ammonium ferrioxalate. Point P represents a composition in which total iron-cyanides are 72% of an amount chemically equivalent to light-sensitive ferric compounds, and in which 50 mol percent of the iron-cyanides are present as ferrocyanide, and 50 mol percent as ferricyanide.' Therefore ferricyanides and ferrocyanides are each 36% chemically equivalent to the lightsensitive ferric compound, from which the relative masses of the respective components readily can t be computed.

Point L represents a. composition containing equimolal quantities of potassium ferrocyanide and potassium ferricyanide, and containing no light-sensitive ferric compounds. It lies on the side AC of the composition triangle. All sensitizers in which 50 mol percent of the iron cyanide compounds are present as ferrocyanides lie on the line LP. 'I'he area NPLC, therefore, includes all sensitlzers in which the total content of ironcyanides equals or exceeds '72% of chemical equivin which half the cyanide of the quantity required to be chemically equivalent to the light-sensitive ferric compound present. and the quantity of ferricyanide is equal to 48% of the quantity required to be chemically equivalent to the light-sensitive ferric compound present. Papers in which the quantity of ferrocyanide is greater than that represented by the line JK, and the quantity of ferricyanide is less than that represented by the line KC, are found t0 be substantially non-bleeding in practice, and

. the quantity of non-pigment-forming substances alence to the light-sensitive ferric compounds nresent, and in which vthe major portion (over mol percent) of the iron-cyanides are present as ferrocyanides.

Point J represents a composition in which the ferrocyanide content is of the quantity required to be chemically equivalent to the lightsensitive ferric compound present, and in which there is no ferrlcyanide. The line (AKJ)4 drawn from this point to A. of which JK is a segment, includes all sensitizers in which ferrocyanide con- -tent is 60% of the ouantitv required to be chemically equivalent tn the light-sensitive ferric compoundpresent. Point K represents a composition in which the ferrocyanide content is 60% required for solubilizing is not excessive. These sensitizers are'included in the area JKC. In all sensitizers included in this area, the major portion of the iron-cyanide compounds are present as ferrocyanide.

The following examples serve to illustrate our invention, although it is to be understood that they are merely examples and no unnecessary limitations are to be assumed therefrom.'

Example I (Point 14) Mass ratio of non-pigment forming substances to iron-cyanide compounds calculated as potassium ferrocyanide 0.60

Example I is a sensitizer containing equal parts by weight of ammonium ferrioxalate and potassium ferrocyanide, and is represented as the midpoint on the line BC.

Instead of using potassium oxalate and potassium carbonate in preparing this sensitizer, and other sensitizers shown as examples hereafter, it is equivalent to use an amount of oxalic acid chemically equivalent to the potassium oxalate shown, and sumcient potassium carbonate to react with the oxalic acid and leave the amount of excess Vpotassium carbonate shown. This is a common practice in the industry and is fully equivalent for every purpose, since the important l factor is not what substances are used in making they are present. In Example I, the use of 6.00 g.

of oxalic acid (H2CzO4.2HzO) and a total of 13.81

g. of potassium carbonate (KaCOs.2I-l'z0) is equivalent to the use of 8.76 g. of potassium oxalate (mCzOcHzO) and 5.53 g. of potassium carbonate; and the reaction between 6.00 g. of oxalic acid and 13.81 g. of potassium carbonate will actually form in the sensitizing solution the same amounts of potassium oxalate, and carbonate ions as the solution of 8.76 g. of potassium oxalate and 5.53 g. of potassium carbonate: with the additional evolution in the case of the reaction between oxalic acid and potassium carbonate of carbon dioxide and the formation of water, neither of which will aii'ect the composition of the sensitizer. It will be understood in the examples which follow that the'same process of forming the actual non-pigment-forming lsubstances desired in the sensitizing solution by 'Ihe sensitizing solutions of Example I and the examples which follow can be used at the concentration shown and will give good results .if so used; or if desired they can be used at greater or lower concentration, within the limits oi solubility of the components of the sensitizer at the coating temperature. So far as the characteristics of non-bleeding and freedom from burnout are concerned, the actual concentration ot pigment-forming and non-plgment-forming substances isimmaterial vso long as the mass ratio of non-pigment-forming substances to ironcyanide compounds, and the percent chemical equivalence of iron-cyanide compounds to lightsensitive ferric compounds are kept within the non-bleed limits'shown in this specmcation.

Example II Point y represents the. following formula: 1. Potassium' qxalate g 8.16 2. Potassium carbonate g-- 4.97 3. Potassium ferrocyanide.. g- 18 4. Ammonium i'errioxalate g-- 27 y 5. Water, jto Baume, degrees-- 14.5

Example III Point 16 represents the same formula as point 15'l except that 3.82 g. of potassium ferricyanide were added.- vThis paper has a printing speed about the same as the usual slow commercial papers. 'lhe total iron-cyanide content is equivalent to 22.90 g. calculated as potassium ferrocyanide; iron-cyanide vcompounds are 179% equivalent' to light-sensitive ierric compounds, and the mass ratio of nonpigment-formlng substances to'to'tal-iron-cyanide compounds calculated as potassium,v Ierrocyanide is 0.60.

Point 16 il1ustrates another convenient characteristic oi this type of diagram. This point lieson a line drawn through A and point 15. Any point lying on this line has a constant ratio of ammonium ferrioxalate to potassium ferrocyanide, namely 27'to 18 or 3 to 2. In general,

vanyline drawn `through one vertex oi the composition triangle represents a constant ratio'of the components `represented by theremaining two vertices. l I -1`- Example IV` `Poi-rit 17 locates the following formula .on the composition triangle: v

rocyanlde Thirty g. of sodium i'errioxalate are equivalent to p 446 Y :SOXm-A of ammonium ferrioxalate.

' Example V Point 18 represents thefflollowing formula: 1. Potassium carbonat`e .....A g..v 2. Potassium oxalate g..- 8.76 3. Potassium ferrocyanide a g.. 15.0 4. Ammonium ferrioxalate-- ..-g.... 30.0 5.- Water to Baum T-degrees 14.5

Percent chemical equivalence of ironcyanide compounds to light-sensitive ferrie compounds -..percen 106 Mass ratio of Vnon-pigment-iorming substances to iron-cyanide compounds calculated as potassium ier-- rocyanide 0.91

Example VI Thev formula represented `bypoint 19 is the same as Example V with the addition 01;.` Potassium ferncyamde 1 `g.; y:0.375

Percent chemical equivalence oi` iron-cyanide V compounds to light-sensitive v.ferrie compounds is 109%. v Mass ratio of non-pigmentforming substances to iron-cyanide compounds calculated as .potassium ferrocyanide is0.88.

I Example Vlr l s Point 20 represents thefollowixigv formula:

21 g. of sodium ferrioxalate are eduiyalentto 446 f (21mm).

or 19.20 g. of ammonium ferrioxalate. Therefore, the sensitizer contains the equivalent of (19.20 plus 3.75) or 22.95 g. of light-sensitive ferric compounds calculated as ammonium 'Ierrioxalata Papers coated with tremely fast.

'I'he following is givenas an ,eirampleoi the" way by which other ferricyanide salts, terrocyanide salts, and light-sensitive compounds than ,f `those shownon thejdiagram may be plotted on 1. Potassium oxalate. .g-- 6.35 2.' Oxalic acid L' r ;g 10.228 3., Potassium. ferrocyanideg-- 18.0 4. Sodiumferrioxalate'- f g.... .30.0v f5. Potassium i'erricyan'iqle....... .....g....4 0.75 6. Water to make ..cc 300 Percent lchemical equivalence ofironcyanidecompounds to light-sensitive ferr-ic c ompounds r spercent.- 146 Mass ratio of non-pigment-forming substances to. iron-cyanide compounds calculated as potassium ferthe diagram. The chemicals and quantities present which may eventuallyenter into the formationof pigment are as -followsz 1. Iron potassium tartrate `(ferrie) .fg.. 30

1. Kmeoicimoe (formas weight 259 which contains one atomic weight of iron).A

446 30 xm-.51.7 lg.`

these sensitizers are exof ammonium ferrioxalate required to be chemically equivalent.

2. `(NH4):Fe(CN) .6Hz0 (formula weight 392 which contains one atomic weight of iron). Y

of ferrocyanide required to be chemically equivalent.

3. Na3Fe(CN).Hz0 (formula weight 299 which contains one atomic weightof iron).

I 8.65 g= 9.2 g. potassium ferricyanide required to be chemically equivalent.

Table IV indicates the calculations required to plot the point.

Table IV Grams Per cent 1. HaFeiOxAHaO 51.7 70.6 2. Fe N 53H10 12.2 10.7 3. KiFeONgn 9.2 12.7 78. 1 100. 0

This is approxlmately point F.

Excellent results are obtained by employing compositions in the area near the non-bleed boundary DFE and the line CB and a particularly important, though limited, embodiment of our invention comprises compositions falling within the shaded area on thegureof the drawing and wherein the weight of non-pigmenti'orming substances, such as buiering agents, solubilizing agents, washing aids, and the like is not in excess of 1.5 times the weight of all of the iron-cyanide salts or. compounds calculated as potassium ferrocyanide (K4Fe(CN) .3H1O) and is preferably equal in weight to or less than the weight of the said iron-cyanide compounds calculated as potassium ferrocyanide. For best results, the total iron-cyanide salt content is at least 80% of that quantity required to be chemically equivalent to the light-sensitive ferrie compound or compounds. 'I'he ferricyanide salt may, for

Point No. 60

Example VIII IX X XI XII tassi oxalate grams 10.92 10.92 10.92 10.921092-6 ggtassigcarbonate d0 3.93 3.93 3.93 3.93 3.93 5 3. Potassiumferrocylnidedo 15.00 15.00 15.00 150015.00 4. Potassium fsn'icyanide -d 0.00 0.56 1.13 1.88 3.00 5. Ammonium ferrioxalate .do 41.00 41.00 41.00 41.0041.00 6. WatertoBaum degrees 19 19 19 19 19 Volume..` .ml 275` 275 275 275 275 Percent chemical equivalence ot 70 mimti "ldt. q liglid e r. pernt 77.3 81.2 `84.8 89.7 97.1 Kerstin of non-pi ent-formmg umwttadwsm um fexrocyanide 0 99 0.94 0.90 0.85 0.79 75 Example' Exam le Exam le XII (point 3i) (point 32) (point 33) .Potassium oxalate .grams.- 20. B4 20. 84 20.94 Potassium carbonate do 7. 86 7. 85 7. 86 Potassium ierrocyanido do 37. 90 37. 90 37. 90 Ammonium ierrioxalate do 20.00 20.00 20.00 Potassium ierricyanide do 3. 54 29.50 Water to Baume degrees.. 16. 5 15. 5 16. 0 Percent equivalence of iron-cyanide compounds to light-sensitive ierrio oomgounds percent.- 400 44.8 800 Mass rat of non-pigment-forming substances to iron-cyanide oomunds calculated as potassium errooyanide 0. 78 0. 70 0. 39

Exam le Exam le X XV (point 34) (point 35) Potassium oxalate grams 20.84 20.94 Potassium carbonato... do.. 7. 86 7. 86 Potasslumierrocyanlde.. o 18.96 28.40 Ammonium ferrioxalate-. do. 20. 00 20. 00 v Potassium ferricyanide do 14. 75 7.3 8

Water to Baume degrees-. 13. 9 i6. l Percent equivalence of iron-cyanide compounds to light-sensitive ferrio com- Mpounds per cent" 400 400 ass ratio of non-pigment-iorming substances l to iron-cyanide compounds calculated as potassium errocyanido 0. 78 0. 78

Example VIII represents the basic solution and contains no ferricyanide salt, as the position of point 8 on the side CB indicates.

Examples IX to X11 represented by points 9 to 12'inclusive are formed by adding quantities of ferricyanide salt to the basic sensitizer represented by point 8. Therefore, all these points lie on a straight line passing through point A.

Paper sensitized by the formula given as Example IX and represented by'point 9 is excep tlonally fast and should, therefore, be used under conditions which take this factor into account.

Points 10, 11 and 12 represent sensitizers which, as indicated hereinabove, are especially satisfactory. These cover a rapid speed range but are readily adapted to present day commercial equip-v ment. Due to non-bleeding and lack of burn- I out. in general', they produce faster printing papers than those produced with the older type of sensitizers containing no ferrocyanide salt. When the customary exposure for the older type is given to these newer papers. a much deeper blue color is obtained without danger of bleeding or of bum-out.

Examples XIII to XVII, inclusive show the eect of increasing greatly the excess of ironcyanide compounds over light-sensitive ferrie iron compounds.

Example XV contains ferrocyanide and ferricyanide 800% of an amount that would be chemically equ'ivalent to the light-sensitive ferrie compounds present. Although this paper is quite slow because of the high concentration of ferricyanide, it is, nevertheless, a usable paper, washes readily and gives non-bleeding prints free from burnout. The mass ratio of non-pigment-forming substances to total iron-cyanide compounds calculated as potassium ferrocyanide is only 0.39 in this sensitizer. Example XIII is a high-speed paper with good color, with good washing characteristics, non-bleeding, and free from burnout. Examples XIV and XVII are somewhat slower butA still well within the speed range of commercial papers. Example XVI is somewhat slower than most commercially used papers, but gives excellent prints, and with Example XV ilbounded by the segment DF oi' the non-bleed boundary, the line FL, and the sides AC and BC desensitizing eiect of the solubilizing salts which are required in much' large concentration in this region as previously discussed. These lines are of the composition triangle. Sensitizers includedv in this area contain an amount oi iron cyanides': at least chemically equivalent to the light-sensi tive ferric compounds present, and contain ferrocyanides as the major pigment-forming ironcyanide compound. Papers prepared from sentitizers representedvby points within this area cannot bleed, because it is not possible to 'form free ferrous iron over an amount chemically equivalent to the iron-cyanide compounds present.

(2) The area NPLC, which includes yall sensitizers containing iron-cyanldes in amounts 72% or more of the quantity chemically equivalent to the light-sensitive ferric compounds present, and containing less than 50 molal percent, oi their (This-is iron-cyanide content as ferricyanide. less than 43.8% of the iron-cyanide compounds as ferricyanides on a mass percent basis ,if the ferrocyanide and ferricyanide are both present in 4their entirety as the potassium. salts.) Such sensitizers contain ferrocyanide salts as thev major pigment-forming iron-cyanide ,compound,'

and are substantially non-bleeding 'in practice without the necessity of loading the sensitizer with non-pigment-forming substances tosecure satisfactory Washing or other characteristics.

3) The area JKC, which includes al1 sensitizers v with content of ferrocyanides 60% or more of the amount chemically equivalent to the lightsensitive ferrie. compounds present, and ferriappropriately called iso-speed lines.

It has been explained heretofore that potassium ferrocyanide, potassium ferricyanide, and ammonium ferrioxalate are used as examples in the description of the accompanying chart, and that. other compounds may be used in place thereof, in quantities that' will provide corresponding chemically equivalent weights, and this lis contemplated in the-accompanying claims..

Weclaim:

` v1. A sensitizer for blueprint papers andthe 7 like, containing a -i'errocyanide salt, af i.'erricyl anide salt, a light-sensitive ferric compound, and nonf-pigment-torming substances,l `in. which 'the totaliron-cyanide content isI at least 72% of that quantity required to lbechemically equivalent to the light-sensitive ferrie compound, and in which the ferricyanide content is less than50 molal 'percent of the total content of iron-cyanide compounds, and in which the weight of-non-pigment- Storming substances is not-more than 1.5 times vthe weightA of all iron-cyanide compounds, calcun lated as potassium ferrocyanide- 2. A `blueprint paper having a sensitizer thereon containing a'ferrocyanide salt, a ferricyanide I' f salt, a light-'sensitiveferric compound, and nonpi'gment-forming substances, in which .the total iron-cyanide content-is at least 72% of the quantity required to be chemically equivalent tothe ylight-sensitive ferric compound, and in which the the weight of al1 iron-cyanide compounds, calcuv I l lated vas potassium ferrocyanide. 1

cyanide content less than 48% of an amount equivalent chemically to the light-sensitive ferric compounds present. Papers sensitized with such sensitizers are substantially non-bleeding in practice wlthout the necessity of loading the sensitizers with non-pigment-forming substances to secure satisfactory washing. In these sensitizers, ferrocyanide salts are the predominant pigment-forming cyanide compounds present.

All papers containing an excess of viron-cyanide compounds over light-sensitive ferrie salts are` non-bleeding, no matter how large the excess of iron-cyanide compounds may be. We have shown formulas for non-bleeding papers containing,

ferrocyanide salts up to 400% (Example XIII) of j quantity required to be chemically equivalent to ferricyanide content is less than 50 molal pers. r Y lcent of the total-content of iron-cyanide compound, and in which Athe weight of non-pigment,- for'ming substances is not more than 1,5 times 3. A method of making blueprints, which con` sists in .coating paper or'the like with a sensitizer containing a ferrocyanlde salt, a ferricyanide salt, a. light-sensitive ferrie compound, and nonpigment-forming substances in which the total l iron-cyanide content is at least '12%01' that the light-sensitive ferrie compound, and in which the ferricyanide, content is less than 50 molal.

' percent of the total content of iron-cyanide 'coml the amount equivalent to light-sensitive ferrlc- I compounds present, which are usable inpresent j commercial practice. Example XV contains tot`al. `VA

iron-cyanide compounds 800% of the 'amount chemically equivalent to light-sensitive ferric compounds present. Further increasesin the ratio of iron-cyanide salts to lightsensitiveferric salts will continue vto give non-bleeding papers.

At present there is no commercial advantage'in using such papers. particularly because-the ex-` 'cess ferrocyanide cannot at present be utilized;

however, such papers are usable and will give prints free from bleeding.

Curved lines a, b, c, d represent approximately equal speed lines. Sensltizers whose-composition is represented by points along any one of these lines all have approximately the same printing speed. 'Ihe curve to the right at the lower portion of these lines is probably due to the following compositions by weight:

' Point. KlFeNnsHlo KiFewN). (NEL).Fe(c,04).-1.1 ,olf Percentk 'Percent n I Percent l A D Y 32s o 67.8 F la 13.0 70.4 `L 56.2 a 43.8 o C 10o o o wherein i the points dening' said 6 5` pounds, and in which the weight'of non-pigmentforming substances is not more than 1.5 times' theweight of all iron-cyanide compounds, calcu-` lated asl potassium i'errocyanide; exposingsaid paper under a design to light, 'and then develop'- ing and washing said paper.

4. A sensitizer for blueprint paper an'd the like I I containing a ferrocyanide salt,ga ferricyanide saltpand a light-sensitive ferrie compound,l the j saidcomposition falling within the area DFLC"l on the ligure ol--the drawing when calculatedjasl I xlr'emeamqmr'etcm,and f- '(Nnmrewlomsmo 5. A sensitizer for blueprint paper and the like containing a `i'errocyanide salt, a ferricyanide area `have the salt, and a light-sensitive ferrlc compound, the said composition. falling within the area NPLC on the gure of the drawing when calculated as K4Fe(CN) 63H20, KaFewN) c.' and wherein the points deiining said area have the following compositions by weight:

Point K|Fe(CN).3H:0 KiFe(CN)| (NH);Fe(C|04);.4H|0

Percent Percent Percent said sensitizer also containing non-pigment- Iorming substances the weight of which is not more than 1.5 times the weight of all iron-cyanide compounds calculated as KAFe(CN) .3Ha0.

6. A se'nsitizer for blueprint paper and the like containing a ierrocyanide salt, a ferricyanide.

salt, -and a light-sensitive ierric compound, the said composition falling within the shaded area on the figure of the drawing when calculated as K4Fe(CN) 3l-120, KaFe(CN) a, and

(NH4)3F(C2O4)3.4H20

said sensitizer also containing non-pigment- .forming substances, the weight oi' which is not more than 1.5 times the weight of all iron-cyanide compounds calculated as K4Fe(CN) 63H20.

7. A sensitizer for blueprint paper and the like containing a ferrocyanide salt, a ferricyanide 'salt, and a light-sensitive ferrie compound, the

said composition falling within the areaJKC on the ilgure of the drawing when calculated as K4Fe(CN) e.3H2O,KaFe(CN) e, and

(NH.) :Fezon 3.41120 wherein the points deiining said area have the following compositions by weight:

Point KiFe(CN).3H,0 KFe(CN) (NHaFewgOmAO Percent Percent y'Percent I 22. l 0 77.9 K 19. 4 l2. l 68. 5 O 100 0 0 pigment-forming substances, the quantity of ierricyanide salt comprising from 2% to 27% by prislng at least 72% of that quantity required to be chemically equivalent to the light-sensitive ferrie compound, and the weight of the non-pigment-forming substances being not in excess of 1.5 times the weight of all iron-cyanide salts calculated as K4Fe(CN)s.3HzO.

10. A sensitizer for blueprint papers and the like containing a ferrocyanide salt, a ferricyanide salt, a 'light-'sensitive ierric compound, and non-pigment-forming substances, the quantity of i'erricyanide salt comprising from about 1% to about 6% by weight oi' the total iron-cyanide salts in the composition. the total iron-cyanide salt content comprising at least 72% of that quantity required to be chemically equivalent to the light-sensitive ierric compound, and the weight of the non-pigment-forming substances weight of the total iron-cyanide salts in the` composition, the total iron-cyanide salt content comprising at least 80% of that quantity required to be chemically equivalent to the lightsensitive ferric compound, and the weight oi.' the non-pigment-forming substances being not. in excess of the weight of all iron-cyanide salts calculated as K4Fe(CN) 63H20.

9. A sensitizer for blueprint papers and the like containing a ferrocyanide salt, a ierricyanide salt, a light-sensitive ferrie compound, and non-pigment-forming substances, the quantity oi' ferricyanide salt comprising from 2% to 27% by weight of the total iron-cyanide salts in the composition. the total iron-cyanide salt content combeing not in excess of 1.5 times the weight of all iron-cyanide salts calculated as K4Fe(CN) 0.31120.

1l. A non-bleeding blueprint paper having a storage life of at least one year under ordinary atmospheric conditions, said paper having a sensitizer thereon containing a ierrocyanide salt, a ferricyanide salt, a light-sensitive ferric compound, and non-pigment-iorming substances, in which the total iron-cyanide salt content is at least 72% of the quantity required to be chemically equivalent to the light-sensitive i'erric compound, the ierricyanide salt content being from 2% to 27% by weight of the total content of the ierrocyanide salt and the ferricyanide salt, and in which the weight of non-pigment-i'orming substances is not in excess of 1.5 times the weightV of both the ferrocyanide salt and the ierrlcyanide salt together calculated as K4Fe(CN) 63H20.

12. A non-bleeding blueprint paper having a storage life of at least one year under ordinary atmospheric conditions, said paper having a sensitizer thereon containing an alkali i'errocyanide salt, an alkali ferricyanide salt, a light-sensitive ferric compound, and non-pigment-forming substances, in which the total iron-cyanide salt content is at least of the quantity required to be chemically equivalent to the light-sensitive ferrie compound, the alkali ferricyanide salt content being froml 2% to 27% by weight of the total content oi the alkali ferrocyanide salt and the alkali ferricyanide salt, and in which the weight of non-pigment-iorming substances is not iny excess of the weight of both the alkali ferrocyanide salt and the alkali ferricyanide salt together calculated as K4Fe(CN)a.3HzO.

13. A non-bleeding blueprint paper having a storage life of at least one year under ordinary atmospheric conditions, said paper having asensitizer thereon containing an alkali metal ferrocyanide, an alkali metal ferricyanide, a lightsensitive ferric compound, and non-pigment forming substances, in which the total iron-cyanide Vsalt content is at least 72% of the quantity required to be chemically equivalent to the light-sensitive ferrie compound, the alkali metal ferricyanide content being from about 1% to about 6% by weight of the total content of the alkali metal ferrocyanide and the alkali metal ferricyanide, and in which the weight of nonpigment-forming substances is not in excess of 1.5 times the weight of both the alkali metal ferrocyanide and thealkali metal ferricyanide together calculated as K4Fe(CN)e.3HzO.

14. A light-sensitive coated paper, said coating containing a ferrocyanide salt, a ferricyanide salt, a light-sensitive ferrie compound, and nonpigment-forming substances, the coating composition ialllng within the shaded area on the ilgure of the drawing whenl calculated as K4Fe(CN) 53H30, K3Fe(CN) s,

(NH4) 3Fe(C2O4) s .4H2`0 and the weight of the non-pigment-forming substances being not more than 1.5 times the weight of both the ferrocyanide salt and the ferricyanide salt together calculated as K4Fe(CN)s.3H2O.

15. A light-sensitive coated paper, said coating containing an alkali ferrocyanide salt, an alkali ferricyanide salt, a light-sensitive ferric compound, and non-pigment-forming substances, the

coating composition falling within the shadedV area on the gure of the drawing when calculated as K4Fe(CN)e.3HzO, KsFe(CN)e, and

(NH4) sFe (C204) 3 .4H2O

the weight of the non-pigment-forming substances being not in excess of the weight of both the alkali ferrocyanide salt and the alkali ferricyanide salt together calculated as KlFeN) 6.3H2o

16. A light-sensitive coated paper, said coating containing a ferrocyanide, salt, a ferricyanide salt, a light-sensitive ferrie compound as pigment-forming substances. and non-pigment-` the ferrocyanide salt and the ferricyanide salt calculated as K4Fe(,CN)e.3H2O.

17. A light-sensitive coated paper, said coating containing a ferrocyanide salt, a ferricyanide salt, a. light-sensitive -ferric compound as pigment-forming substances, and non-pigmentforming substances, the ferrocyanide comprising between 25% and 27% by weight of the total pigment-forming substances, the ferricyanide salt comprising up to 6% by weight of the pigment forming substances, and the weight of the non-pigment-forming substances being not more than 1.5 times the weight of both the ferrocyanide salt and the ferricyanide salt together calculated as K4Fe(CN)e.3H2O.

18. A method of making blueprints which com-- prises coating paper or the like with a sensitizer containing a ferrocyanide salt, a ferricyanide salt, a light-sensitive ferric compound, and nonpigment-forming substances. said composition` falling within the area DFLC on Vthe ligure of the drawing when calculated as K4FeiCN) 63H20, K3Fe(CN) s, and (NH4)3Fe(C204)a.4H20, wherein the points defining said area have the following compositions by weight:

exposing said coated paper under a design to light, washing, oxidizing, again washing, and then drying said paper.

19. A method oi' making blueprints and the like which comprises coating paper or the like with a sensitizer containing a ierrocyanide salt.

a ferricyanide salt. a light-sensitive ferrie compound, and non-pigment-ioming substances, said composition falling within the area NPLC on the ligure of the drawing when calculated as KiFe( CN) 63H20. K3Fe(CN) s, and

wherein the points defining said area have the following compositions by weight:

Point K4Fe(CN)e.3H2O 'K3Fe(CN)| (NHxFo(Cz0a)a-4Ha0 Percent Percent Percent 25.4 0 74.6 13.1 10.2 76.7 56.2 43.8 0 0 0 the weight of the non-pigment-forming substances being not in excess of the weight of all iron-cyanide compounds calculated as exposing said coated paper under a design to light, washing, oxidizing, again washing, and then drying said paper.

20. A method of making blueprints and the l the iigure of the drawing when calculated as wherein the points defining said area. have the following compositions by weight:

Point KiFe-(CNhHgO K3Fe(CN)a (NH4) Fe(0104)|.4H|0

Percent Percent Per: J. 22. 1 0 77. 9 K 19. 4 12. 1 88. 5 0....A I 100 0 0 'the weight of the non-pigment-forming sub- (NH4) 3FG (C204) 3.4H2O

the weight oi' the non-pigment-forming substances being not in excess of all iron-cyanide compounds vcalculated as K4Fe(CN)s.3HzO,vex posing said paper under a design to light, washing, oxidizing, again washing, and then drying said paper.

` CLYDE A. CROWLEY.

GEORGE H. GOODYEAR 

